ABSTRACT Marijuana policy analysis has taken on new urgency with widespread medical marijuana legislation and, more recently, recreational legalization in an increasing number of states. The state of Washington voted to legalize recreational marijuana in November of 2012, however, time was allowed to implement a regulatory framework and retail stores did not open until July of 2014. Our team at the Alcohol Research Group was funded by NIAAA to conduct a series of six cross-sectional representative surveys of Washington during 2014, 2015 and 2016 with longitudinal follow-ups of selected respondents. While the focus of these surveys was alcohol use and purchasing in relation to the privatization of the state liquor monopoly, a section on marijuana use behaviors, purchasing, attitudes and problems was also included. We now propose to utilize these surveys to investigate effects of recreational legalization and local policy implementation, linking data on marijuana store locations and other area measures at the time of each survey wave with respondent addresses and ZIP-codes. The pattern of store openings occurred gradually during our survey period, going from 0 at Wave 1, 120 at Wave 3 and 311 at Wave 6. Planned analyses consider a range of important topics including: estimation of market size and the proportion captured by legal retail; risks for a variety of marijuana-related outcomes; relationships between an individual?s marijuana, alcohol and tobacco use over time; and area-level analyses on associations of outlet locations and retail characteristics with marijuana use and problems. Detailed measures of use behaviors include frequency, amount, intensity, ingestion method and context of use, as well as use with alcohol, tobacco, and/or other drugs. Importantly, panel analyses will estimate the effects of changing gravity access measures based on driving time to the nearest store locations on use and problem measures within individuals over time. Building on our prior studies of problems associated with simultaneous co-use of alcohol and marijuana, the proposed study will consider impacts of marijuana legalization on the use and co-use of marijuana with alcohol, tobacco and other drugs, as well as resulting problems. Innovative measures of the legal and illicit purchasing behaviors include products, amounts, prices, frequencies and sources. Our analyses will utilize these measures to estimate the size of Washington?s marijuana market in grams and dollars and track the shift towards legal retail sales. Analyses of legalization and store opening impacts will also include potentially marijuana-related injury mortality rates for all Washington counties from 2008 to 2018. Gender- and age-specific estimates will be used to evaluate impacts of county retail availability, outlet clustering and sales. This project will provide a wealth of new information relevant to impacts of legalization and local marijuana regulation, as well as inter-relationships between marijuana and other substance use problems over time. This information will be of great relevance to policymakers, who are increasingly faced with the task of formulating federal, state and local policy approaches to marijuana.